Who has been buying The Kosei Securities Co., Ltd. stock?

7 distinct investors have filed 25 disclosed large-shareholding filings in The Kosei Securities Co., Ltd. (8617), most recently on 2026-01-05. Each filer, their role, the number of shares and the price at filing are listed in the table on this page.

How many insider filings does The Kosei Securities Co., Ltd. have?

The Kosei Securities Co., Ltd. has 25 buy-side and 23 sell-side disclosures on record, covering ¥2.3B ($15.0M) in total reported value, spanning 2022-02-21 to 2026-01-05.

Where does StockDrifts get The Kosei Securities Co., Ltd. insider data?

From EDINET large-shareholding (5%+) reports — the official filing system run by the Financial Services Agency (Japan). StockDrifts parses each disclosure and matches it to daily price history; the original filings remain available directly from EDINET.

Do insider buys in Japanese stocks predict returns?

Not uniformly. StockDrifts scored 101,000+ Japanese large-shareholding filings on fixed 12-month forward returns and found the predictive power concentrated in specific filer types and filing patterns rather than spread evenly across all disclosures.

The Kosei Securities Co., Ltd. 8617

Company

光世証券株式会社The Kosei Securities Co., Ltd.

Investors

Buys

Total Value

¥2.3B ($15.0M)

Avg Return

+23.00%

Last Filing

2026-01-05

The Kosei Securities Co., Ltd. (8617) has 25 disclosed large-shareholding filings and 23 disclosed disposals on record, filed by 7 distinct investors. Together those filings cover ¥2.3B ($15.0M) in reported transaction value. The earliest filing StockDrifts holds for The Kosei Securities Co., Ltd. is dated 2022-02-21; the most recent is 2026-01-05. All of it is parsed from EDINET large-shareholding (5%+) reports, the official disclosure system operated by the Financial Services Agency (Japan). Across these filings the average return since disclosure is +23.00%, measured from each filing date to the latest available close.

Price & insider activity (12 months)

Recent filings

Date	Type	Source	Insider	Purpose	Shares	Price at filing	Return	Value
2026-01-05	BUY	unknown	株式会社哲学の道文庫	strategic	912.1K	¥466	-21.0%	¥514M ($3.3M)
2026-01-05	SELL	unknown	株式会社巽事務所	strategic	1.1M	¥466	-21.0%	¥627M ($4.0M)
2026-01-05	SELL	unknown	株式会社巽也蔵	strategic	1.9M	¥466	-21.0%	¥1.1B ($6.9M)
2025-11-18	BUY	Market Buy	巽春菜 Haruna Tatsumi	strategic	299.0K	¥455	+24.0%	¥96M ($618K)
2025-11-18	BUY	Market Buy	巽大介 Daisuke Tatsumi	strategic	540.4K	¥455	+24.0%	¥7M ($45K)
2025-11-11	BUY	unknown	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.9M	¥461	+22.3%	¥437K ($3K)
2025-11-11	BUY	unknown	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	912.1K	¥461	+22.3%	¥420M ($2.7M)
2025-11-11	SELL	unknown	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.2M	¥461	-22.3%	¥143M ($920K)
2025-11-10	BUY	Market Buy	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	912.1K	¥470	+20.0%	¥429M ($2.8M)
2025-11-10	BUY	Market Buy	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.6M	¥470	+20.0%	¥80M ($515K)
2025-11-10	BUY	Market Buy	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.9M	¥470	+20.0%	¥31M ($198K)
2025-08-19	BUY	Market Buy	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	912.1K	¥495	+13.9%	¥451M ($2.9M)
2025-08-19	BUY	Market Buy	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.9M	¥495	+13.9%	¥49M ($315K)
2025-08-19	BUY	Market Buy	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.4M	¥495	+13.9%	¥684M ($4.4M)
2025-06-05	BUY	Market Buy	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.8M	¥411	+37.2%	¥41M ($262K)
2025-06-05	BUY	Market Buy	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	912.1K	¥411	+37.2%	¥375M ($2.4M)
2025-06-05	BUY	Market Buy	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.4M	¥411	+37.2%	¥568M ($3.7M)
2025-04-24	BUY	unknown	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	912.1K	¥390	+44.6%	¥356M ($2.3M)
2025-04-24	BUY	unknown	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.4M	¥390	+44.6%	¥58M ($377K)
2025-04-24	SELL	unknown	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.7M	¥390	-44.6%	¥58M ($377K)
2024-10-30	SELL	unknown	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.2M	¥398	-41.7%	¥88M ($568K)
2024-10-30	BUY	unknown	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.8M	¥398	+41.7%	¥725M ($4.7M)
2024-10-30	BUY	unknown	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	912.1K	¥398	+41.7%	¥363M ($2.3M)
2024-10-29	BUY	Market Buy	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	912.1K	¥407	+38.6%	¥371M ($2.4M)
2024-10-29	SELL	Market Buy	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.5M	¥407	-38.6%	¥37M ($237K)
2024-10-29	BUY	Market Buy	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.8M	¥407	+38.6%	¥87M ($563K)
2024-05-08	SELL	unknown	日興アセットマネジメント株式会社 Nikko Asset Management Co.,Ltd.	other	21.9K	¥637	+11.5%	¥11M ($74K)
2024-05-08	BUY	unknown	三井住友トラスト・アセットマネジメント株式会社 Sumitomo Mitsui Trust Asset Management Co.,Ltd.	other	408.8K	¥637	-11.5%	¥257M ($1.7M)
2024-01-25	SELL	unknown	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	912.1K	¥590	+4.4%	¥6M ($40K)
2024-01-25	BUY	unknown	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.5M	¥590	-4.4%	¥46M ($296K)
2024-01-25	SELL	unknown	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	912.1K	¥590	+4.4%	¥6M ($40K)
2024-01-25	BUY	unknown	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.5M	¥590	-4.4%	¥46M ($296K)
2024-01-25	SELL	unknown	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.6M	¥590	+4.4%	¥108M ($697K)
2024-01-25	SELL	unknown	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.6M	¥590	+4.4%	¥108M ($697K)
2023-09-05	BUY	Market Buy	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	922.1K	¥626	-9.9%	¥577M ($3.7M)
2023-09-05	SELL	Market Buy	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.5M	¥626	+9.9%	¥94M ($605K)
2023-09-05	BUY	Market Buy	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.8M	¥626	-9.9%	¥94M ($609K)
2023-09-04	BUY	unknown	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.6M	¥632	-10.8%	¥95M ($611K)
2023-09-04	BUY	unknown	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	922.1K	¥632	-10.8%	¥583M ($3.8M)
2023-09-04	BUY	unknown	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.6M	¥632	-10.8%	¥95M ($611K)
2023-09-04	BUY	unknown	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	922.1K	¥632	-10.8%	¥583M ($3.8M)
2023-09-04	SELL	unknown	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.6M	¥632	+10.8%	¥127M ($816K)
2023-09-04	BUY	unknown	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.6M	¥632	-10.8%	¥1.0B ($6.7M)
2023-08-28	BUY	unknown	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	922.1K	¥586	-3.8%	¥540M ($3.5M)
2023-08-28	BUY	unknown	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.5M	¥586	-3.8%	¥152M ($983K)
2023-08-28	SELL	unknown	株式会社巽也蔵 tatumiyagura CO.,LTD	strategic	1.6M	¥586	+3.8%	¥117M ($757K)
2023-02-24	SELL	unknown	巽春菜 Haruna Tatsumi	strategic	88.0K	¥389	-45.0%	¥31M ($200K)
2023-02-24	BUY	unknown	株式会社哲学の道文庫 Tetsugaku no Michi Bunko Co., Ltd.	strategic	922.1K	¥389	+45.0%	¥359M ($2.3M)
2023-02-24	BUY	unknown	株式会社巽事務所 Tatsumi Office Co., Ltd.	strategic	1.5M	¥389	+45.0%	¥101M ($652K)
2023-02-24	BUY	unknown	巽大介 Daisuke Tatsumi	strategic	525.4K	¥389	+45.0%	¥202M ($1.3M)

Showing the 50 most recent of 74 filings.

Frequently asked questions

Who has been buying The Kosei Securities Co., Ltd. stock?: 7 distinct investors have filed 25 disclosed large-shareholding filings in The Kosei Securities Co., Ltd. (8617), most recently on 2026-01-05. Each filer, their role, the number of shares and the price at filing are listed in the table on this page.
How many insider filings does The Kosei Securities Co., Ltd. have?: The Kosei Securities Co., Ltd. has 25 buy-side and 23 sell-side disclosures on record, covering ¥2.3B ($15.0M) in total reported value, spanning 2022-02-21 to 2026-01-05.
Where does StockDrifts get The Kosei Securities Co., Ltd. insider data?: From EDINET large-shareholding (5%+) reports — the official filing system run by the Financial Services Agency (Japan). StockDrifts parses each disclosure and matches it to daily price history; the original filings remain available directly from EDINET.
Do insider buys in Japanese stocks predict returns?: Not uniformly. StockDrifts scored 101,000+ Japanese large-shareholding filings on fixed 12-month forward returns and found the predictive power concentrated in specific filer types and filing patterns rather than spread evenly across all disclosures.

Source filings

Every trade listed above is disclosed in EDINET large-shareholding (5%+) reports, filed with the Financial Services Agency (Japan). View the original EDINET filings for The Kosei Securities Co., Ltd.. For how StockDrifts scores these disclosures, see the Japan insider signal tier research, or browse every Japanese stock we track.